Peel and steam the sweet potato. When ready mash it into a puree.
In the meantime, mix the wet ingredients in a medium bowl : rice milk with the apple vinegar, maple syrup and coconut oil and let it sit while preparing the dry ingredients.
Grind the oat flakes into flour using preferably a high speed blender (or use oat flour or rice flour). Pour into a large mixing bowl.
Add to this large mixing bowl the remaining dry ingredients and mix well with wooden a spoon.
Mash the sweet potato. Add all the wet ingredients including the mashed sweet potato to the dry ingredients and mix it well with a spoon or a whisker until it looks smooth. Let it sit at least for 15 minutes.
If the batter is too thick then add 1-2 Tbsp of rice milk and mix again.
Preheat the waffle maker and grease it with coconut oil.
Bake the waffles until golden brown.